HM Revenue and Customs will see this property as an investment; your father's occupation of the house and the lack of rent paid are irrelevant. You will pay CGT on the difference between the sale and purchase price, less your legal and agency costs, stamp duty, and any repairs and improvements you can prove you have made in the eleven years (e.g. new boiler). You can also reduce the amount liable for tax using the old "indexation" (inflation proofing) tax relief, for the period up to April 1998. There are tables to work this out online � see dyerpartnership.com/capgain.html#indexation.
For the period after April 1998, the new "taper relief" system reduces your chargeable gains still further by 5% for every complete year, with an extra year because your purchase occurred before April 1998. You will therefore get nine years of taper relief, which means a 45% reduction in your chargeable gain. You also get an annual CGT allowance which is something like �8400 before you pay tax.
So, some sample figures:
Original purchase price �80,000
Sale price �240,000
Costs incurred for sale and purchase: �6,000
Maintenance costs: �6,000
So net chargeable gain = �148,000
Reliefs:
Indexation - 3 years from April 1995 - 98 = 9.1%
Taper relief - 8+1 years = 45%
So chargeable gain after reliefs = �67,932
Tax allowance = �8,800
So you would pay CGT at 40% on just under �60K, which is about �24,000.